Wildlife photography and writing from naturalist Rebecca Gibson.

Camouflage in Psittacosaurus

It’s always a delight when I stumble across a dinosaur story in the news. These genuine legends will be part of modern society forever, I’m convinced of it.

Yesterday I read a story of Psittacosaurus (“parrot-lizard”), a herbivorous creature that roamed forests in parts of China, Mongolia, Russia and potentially Thailand during the Early Cretaceous period, about 130 to 100 million years ago. Despite its distinct lack of horns, it belonged to the same group as Triceratops:Ornithischia, meaning “bird-hipped”. Its name comes from its thick beak, as a result of the prominent rostral bone at the tip of its upper beak. It is a peculiar creature in that it chewed its vegetative food like a mammal, but then ground up the tougher matter with stones in its gizzard, a common feature found in birds and reptiles such as crocodiles, that forms part of their digestive system.

Being herbivorous and lacking the teeth and claws to defend itself, Psittacosaurus needed a way of defence. As seen in penguins and some species of dolphins, Psittacosaurus was darker on top and lighter underneath. This form of camouflage is known as countershading, and effectively disguises the animal by offsetting its shadowing. Dark parts of the animal’s body are exposed to bright sunlight, while paler parts are exposed to shade. This shading provides a contrast to usual light-to-dark gradient of natural illumination. The effect makes the animal flatter and without depth, obscuring its outline to potential predators.

It is understandable to think it impossible for scientists to know if Psittacosaurus demonstrated counter shading without being able to see its skin. However, recent evidence into the preserved pigments in the dinosaur’s fossils has indicated that there was a pattern in the distribution of melanin; more on the animal’s back than its belly, thus proving its countershading camouflage.

In response to this new evidence, scientists have created a life-size model of Psittacosaurus, with the help of palaeo-artist Bob Nicholls, to see how its camouflage helped it survive in its forest habitat. The findings have been published in Current Biology journal. One of the authors, Dr Jakob Vinther, said that this kind of investigation “can provide not only a better picture of what extinct animals looked like, but they can also give new clues about extinct ecologies and habitats”.